The present disclosure relates to developing apparatuses that are suitably used for image forming apparatuses such as copy machines and printers, and image forming apparatuses having the developing apparatuses mounted therein.
To date, developing devices for use in image forming apparatuses have been known. The developing device includes: a development housing having a developing roller and an agitating screw; and a toner container that is detachably mounted to the development housing for supplying toner. A toner outlet is formed in a bottom portion of the toner container so as to be openable and closable, and a toner supply inlet is formed in the development housing at a position corresponding to the toner outlet. When the toner container is mounted to the development housing, and the toner outlet and the toner supply inlet are opened, toner in the toner container is supplied into a predetermined circulation-conveying path formed in the development housing.
The circulation-conveying path includes a forward conveying path for the toner supply inlet, and a return conveying path for the developing roller. In each conveying path in the circulation-conveying path, an agitating screw having helical blades provided around a rotation shaft is mounted. Toner is circulated and conveyed, by the agitating screws, in and between the forward conveying path and the return conveying path.
In the developing device having such a structure, a conveying capability reduction portion configured to locally reduce conveying capability is provided, downstream of the toner supply inlet, on the downstream side of the agitating screw disposed in the forward conveying path. Due to the conveying capability reduction portion, an accumulation portion for toner is formed, near the toner supply inlet, upstream of the conveying capability reduction portion. When an amount of toner is increased in the accumulation portion, the toner supply inlet is blocked with toner in the accumulation portion. On the other hand, when an amount of toner is reduced in the accumulation portion, a gap is generated between the toner supply inlet and the accumulation portion for toner, and toner enters the development housing from the toner container. Thus, an amount of toner to be additionally supplied from the toner container into the development housing is adjusted according to an amount of toner accumulated in the accumulation portion.